This summer, more than 2 million visitors will enjoy the high peaks and mountain meadows of Rocky Mountain National Park in northern Colorado. Packaged in their air-conditioned cars and yearning for the next rest stop, very few of them will notice that those meadows have lost some of their color. But in alpine tundra areas in and near the park, wildflowers have given way to grass. The cause? Nitrogen deposition, a byproduct of air pollution.

Seventy percent of the nation’s parks have cleaner air today than they did a decade ago, according to a report recently released by the National Park Service. But the Interior West’s parks have been left out of the party. From Glacier National Park in northern Montana to Bandelier National Monument in New Mexico, their air is clouded with increasing levels of ammonium, sulfates, nitrates and ozone.

Rocky Mountain National Park wants to do something about it. This spring, the National Park Service, the Colorado Department of Public Health and Environment, and the Environmental Protection Agency formed the Rocky Mountain National Park Initiative to reduce pollutants in the park. In a recent letter to state health officials, Park Superintendent Vaughn Baker set an ambitious goal: slashing nitrogen deposition in half, to a level that probably hasn’t been seen since the 1950s.

Although Baker’s letter carries no regulatory authority, it’s being hailed as "historic" by environmentalists, coming from an agency that in recent years has been known for keeping its organizational mouth shut on such issues. Indeed, it’s the first time an individual park has worked with regulators to tackle air pollution. "The question now is whether it will result in real policy change," says Vickie Patton, senior attorney for Environmental Defense.

In the past, park pollution problems have resulted in policy changes on a regional level. In 1991, motivated by the thickening cloud of smog over Grand Canyon and other Western parks, Congress created the Grand Canyon Visibility Transport Commission, composed of the governors of Western states, and charged it with developing a plan to combat haze on the Colorado Plateau (HCN, 6/28/93: The blurring of the West). Since 1996, when the commission made its recommendations, Western power plants have reduced sulfur dioxide emissions by more than 35 percent. And federal regulations, spurred in part by the commission’s work, have reduced nitrate emissions from mobile sources such as automobiles by 70 percent.

But those reductions haven’t kept up with a host of other haze-inducers, including dust, wildfire smoke and even pollutants from as far away as China. "There are things we can do something about, and other things like wildfire that we can’t control," says Patrick Cummins, co-director of the Western Regional Air Partnership, the organization charged with carrying out the commission’s recommendations. Emissions from the booming oil and gas industry — primarily in the form of volatile organic compounds, or VOCs, and nitrogen oxide, two main ingredients of ozone — are an "emerging issue," says Cummins, "and one we’re trying to get our hands around" (HCN, 10/31/05: Oil and gas drilling clouds the West's air).

On Colorado’s Front Range, where the Denver metro area sprawls across the foothills and plains below Rocky Mountain National Park, regulators are considering tightening their grip on those emissions in response to dangerously high ozone levels. The energy boom has outpaced regulations, according to Michael Silverstein of the Colorado Department of Health. Energy industry sources are expected to contribute 236 tons of VOCs per day to the air next year in the Denver area, making it the largest man-made source. "We have got to get that down to a manageable level — about 90 tons per day," Silverstein says.

Although the proposed regulations are not a direct response to problems at Rocky Mountain National Park, they should help alleviate the park’s ozone problems. But that’s only one piece of the pollution equation. The park is currently experiencing 15 times the natural levels of nitrogen deposition — twice the critical load. Nitrogen acts as a fertilizer, but when it surpasses critical levels, it encourages the growth of grasses and sedges. Those plants choke out wildflowers, throwing the ecosystem out of balance. About half of the park’s nitrogen deposition comes from ammonia, which falls out of the air to the earth and water. The rest is from nitrogen oxides, mostly from fuel combustion.

According to Silverstein, agricultural sources account for about 50 percent of the ammonia emissions on the Front Range. Agricultural emissions tend to be generated over a large area of land — nitrogen fertilizer on fields, for example, or feedlots filled with cattle — rather than from a tailpipe or smokestack. This makes regulation and monitoring more difficult. Further complicating the issue is the possibility that significant levels of ammonia emissions may come from outside the state.

The Rocky Mountain National Park Initiative has begun working on these and other air quality issues, and has launched a study to better pinpoint ammonia sources. Meanwhile, park officials hope other parks around the region will follow their example. "We can turn this boat around, because we caught it before it went too far," says Karl Cordova, a biologist at Rocky Mountain National Park. "Working together, we can make things happen. No agency can solve this alone."